1.5 the immune system

• pathogen: an agent, especially a virus or a bacterium, that causes disease
• vector: an organism, such as a mosquito or flea, that carries disease-causing pathogens from one person to another
• antiseptic: a solution or substance that prevents or inhibits the growth of micro-organisms
• protozoan: a group of microscopic, single-celled organisms that each have a nucleus. many disease-causing protozoans can only divide within a host organism
• fungi: organisms that absorb food in solution directly through their cell walls and do not conduct photosynthesis; reproduction occurs through spores
• bacteria: microscopic, single-celled organisms that lack a membrane-bound nucleus and membrane-bound organelles; reproduction is chiefly by cell division to produce identical daughter cells
• antibiotic: a drug that fights bacterial infections
• virus: a non-cellular particle consisting of a protein coat surrounding genetic material that multiplies only within the cells of a living organism
• antiviral drug: a type of medication that controls or cures an infection from a virus
• antigen: a complexmolecule on the surfaceof an invading pathogenthat triggers an immuneresponseIt is short for antibodygenerator.
• macrophage: a typeof white blood cell thatengulfs dead cells, cellulardebris, and foreign cellsIt presents pathogenicantigens to T-cells in theimmune response
• T-cell: a type of whiteblood cell that matures inthe thymus glandIt recognizes and destroysinvaders or releaseschemical messengers toco-ordinate the immuneresponse
• helper T-cell: a type ofT-cell that co-ordinatesthe actions of other cellsinvolved in the immuneresponseIt sends chemicalmessages to activate theantibody producing B-cellsand killer T-cells.
• B-cell: a type of whiteblood cell that producesantibody molecules whenstimulated by helperT-cells
• antibody: a proteinmolecule produced by aB-cell designed to bindto a specific antigen tofacilitate its destruction
• killer T-cell: a type ofT-cell that recognizes anddestroys body cells byreleasing proteins thatcreate large holes in thetarget cell’s membrane
• memory B-cell andmemory T-cell:specialized white bloodcells that persist in thebloodstream to providefuture immunity to invadersbearing a specific antigen
• suppressor T-cell: a type of T-cell that sends chemical messengers to stop the immune response to an antigen
• vaccination: an injection that exposes the body to the antigens from disease-causing pathogen so that memory cells and antibodies can be made to provide immunity
• inoculation: a process of producing immunity by introducing antigens of an infectious agents through a cut in the skin's surface
• autoimmune disease: a disorder in which the immune system produces antibodies against the body's own cells. (multiple sclerosis, lupus, type-1 diabetes, rheumatoid arthritis)